The role of calcium and zinc in metallo-enzymes has often been difficult to investigate because these ions are transparent to UV- VIS radiation. Over the last fifteen years techniques have been developed to replace calcium by the lanthanide ions in order to learn about the domain interactions surrounding the metal ion center. This proposal involves fundamental studies of the differences within the lanthanide series and the effect these differences will have on calcium replacement studies. Among the techniques to be used in these studies of metal ions in solution are UV-VIS spectroscopy, FT-IR, FT-NMR, ultrasonic absorption, polarography, temperature jump and stopped flow in order to better characterize both enzyme model systems and enzymes in solution. Ultrasonic absorption measurements have not only been utilized to measure the kinetics of reactions at zinc centers, but in addition they have provided a sensitive measure of changes in geometry or conformation around zinc in solution. We will attempt to apply the ultrasonic relaxation technique to two zinc- enzyme systems, carbonic anhydrase and carboxypeptidase A, both of which have been well characterized with other techniques. If ultrasonic measurements provides meaningful data for these two enzyme systems, then future efforts will be involved in applications using less-well known enzymes. Another biochemical system to be investigated is the interaction between +7,8-diol- benzo(a)pyrene with DNA using the temperature jump technique (with Professor Becker). Another problem of major concern involves actinide chemistry, especially with regard to whether or not replacement of the radioactive actinides by the non- radioactive lanthanides will result in similar chemical results, thereby allowing studies of the interactions of actinides with biological molecules to be carried out through lanthanide replacement. Both the model system studies and the enzyme investigations should provide significant information concerning the roles of metal ions in systems of biochemical importance.